The hydroformylation reaction is useful in the preparation of aldehyde products by the reaction of one mole of olefin with one mole each of hydrogen and carbon monoxide. The reaction has been especially useful in the preparation of normal and iso-butyraldehyde from propylene. These materials, in turn, are converted into many commercially significant chemical products such as, for example, n-butanol, 2-ethylhexanol, n-butyric acid, iso-butanol, neo-pentyl glycol and the like. These products alone represent a multi-billion dollar market worldwide. Additionally, the hydroformylation of alpha-olefins such as 1-octene, 1-hexene and 1-decene yield aldehyde products that are useful feedstocks for the preparation of detergent alcohols. The linear carbon-chain alcohol products are particularly desirable for use in detergent grade products. The hydroformylation of allyl alcohol is used commercially as a route to 1,4-butanediol. In this use of the hydroformylation reaction, it is desirable to obtain aldehyde products where the formyl group is added to the terminal position of the olefin thus obtaining linear carbon-chain aldehyde products.
U.S. Pat. No. 3,527,809 discloses a low pressure and low temperature process that utilizes rhodium catalysts. Since this disclosure, numerous improvements have been made to increase both the activity and the product ratio with a heavy emphasis on yielding linear aldehyde product. However, there is a substantial potential market for derivatives of branched-chain aldehydes, as well as the existing large market for linear aldehyde hydroformylation products.
One disadvantage of known hydroformylation catalysts is that they produce aldehydes with a narrow linear-to-branched (or normal-to-iso) product ratio, regardless of the process conditions employed. Thus, there is a need for catalysts that can yield different n/iso product ratios on demand in a single reactor in order to reduce capital costs, increase the degree of utilization of capital equipment, and more efficiently use reactant feed gases.
Surprisingly, we have found a class of compounds that allows us to widely vary the ratio of butyraldehyde products by varying process conditions such as the hydrogen and carbon monoxide partial pressures, temperature, or inert gas partial pressure.